Rationale:The purpose of this research study is to test the effectiveness of the standard high dose cytarabine (HiDAC) on days 1 through 5 followed by a single dose of pembrolizumab on day 14 as induction therapy in patients with relapsed and refractory acute myeloid leukemia (AML). Patients who achieve a response to treatment will continue on the study drug (pembrolizumab) every 3 weeks for up to 2 years maintenance therapy.